Three different breeds of 20 each six monthe old earmarked gilts of known genetic background will be bred so as to make available approximately 800 piglets a year. The serum cholesterol levels of the gilts, the purebred boars and their progeny will be compared in order to determine the extent of genetic variability in serum lipid levels in each family. Two types of diets will be used in this study. In one, the development of raised plaques will be maximized by including known and presently suspected atherogenic factors in the diet. The siblings will be sacrificed at six months of age, the heart and aorta removed and the aorta divided into two sections; one for pathological and one for chemical analyses. The aortas will be stained with Rhodamine 6G, the lipid-involved areas visualized under ultraviolet light and separated from the uninvolved areas. The lipid composition and the enzyme activity in the involved and uninvolved areas will be compared. The pathological studies will be carried out with the cooperation of Dr. H. Imai of the Albany Medical School. The results of the pathological and biochemical studies will be correlated in order to provide a possible means of averting atherosclerosis.